In this paper, a novel threshold selection algorithm for the 60 GHz TOA (time of arrival) estimation is proposed. It exploits the skewness, kurtosis, standard deviation and curl of the received (Energy Detector) ED based samples. The best threshold values for different signal to noise ratio (SNR) are investigated via simulations. The proposed ED based technique has low complexity, sampling rate requirements, and high accuracy compared with other ED based algorithms.
We propose relaxed computation for the non-bifurcation progressive disaster recovery problem. When massive failure occurs, failed components are gradually repaired since repair resources are limited. Though there are studies on disaster recovery problem to maximize the amount of recovered traffic considering this assumption, they are based on the maximum flow approach, where traffic bifurcation on an arbitrary node is allowed. This condition is not practical in an actual environment. We first formulate non-bifurcation progressive disaster recovery problem as 0-1 integer linear programming. Because the problem is NP-hard, we present a problem-decomposition method and obtain an improvement of 13% over the benchmark method.
Chaos multiple-input multiple-output (C-MIMO) transmission scheme is a Gaussian modulation-based block transmission scheme that achieves both channel coding effect and physical layer security. Further, channel coding gain is obtained by concatenating a channel code to a C-MIMO that has a sequential log likelihood ratio (LLR). However, the sequential LLR is quasi-optimal and has slight performance degradation. Therefore, we propose a symbol-unit maximum a posteriori (MAP) decoding to calculate an optimal LLR for C-MIMO. The improved performance of the proposed scheme is demonstrated through numerical simulations.
Chaos multiple-input multiple-output (C-MIMO) is a transmission scheme that uses Gaussian signal transmission based on chaos, where physical-layer security and channel coding effect are obtained. However, because the Gaussian signals are generated according to the principle of central limit theorem, about ten independent chaos signals are needed, resulting in increased calculation complexity. In addition, the probability density function of the phase of transmit signals slightly deviates from uniform distribution, which degrades the bit error rate (BER) performance. Therefore, we propose a C-MIMO scheme with improved Gaussian modulation, in which the stochastic characteristic is improved by applying the Box–Muller method with only one chaos signal.
This paper proposes a new Zero-Padded CAZAC sequence by using a discrete chirp signal and proves mathematically that the proposed Zero-Padded CAZAC sequence satisfies the original properties of constant amplitude and zero-autocorrelation in the time domain. This paper also demonstrates the effectiveness of proposed Zero-Padded CAZAC sequence by using computer simulation results when employing it as a preamble symbol in the channel estimation method for the OFDM signal with a non-Nyquist sampling rate in the non-linear and multipath fading channels.
The coding problem over wiretap channels is to realize an encoder and a decoder such that the legitimate receiver can correctly decode transmitted secret messages while the eavesdropper knows little about the secret messages. Traditionally, the secrecy of messages to the eavesdropper has been measured in terms of mutual information. Recently, several researches on the wiretap channels employ the bit error rate after decoding by the eavesdropper as a secrecy measure. In this note, we show that the secrecy capacity with respect to the bit error rate criterion is different from that with the traditional mutual information criterion. In addition to that, the encoder can be deterministic for the bit error rate criterion, while it must be stochastic for the mutual information criterion.
This paper proposes a subjective assessment test procedure that quantifies speaker identification accuracy of bandwidth-limited speech. To quantify such accuracy, it is common to conduct a subjective assessment test and regard the correct answer rate as speaker identification accuracy. In such a test, the following two requirements should be met. (1) Conduct an experiment in which stable assessment is executed over time and (2) obtain an evaluation value that has little dependence on the degree of identification difficulty of the unprocessed speech used in the test as speaker identification accuracy. Our proposed subjective assessment test procedure takes the above requirements into account. We show that the proposed test procedure is effective in quantifying speaker identification accuracy of bandwidth-limited speech by verifying the validity of this procedure from obtained test results.
This paper presents a calibration method for measuring the channel capacity using a three-dimensional multiple-input multiple-output (MIMO) Over-The-Air (OTA) apparatus. The reference level is calibrated to establish the Gaussian angular power spectra in elevation in consideration of various power losses that exist in the fading emulator. The measured results of MIMO channel capacity agree well with the analytical outcomes calculated by Monte Carlo simulation, demonstrating that the proposed calibration method gives a high degree of accuracy for measuring the channel capacity using the three-dimensional MIMO-OTA apparatus.